A number of catalysts have been developed and/or used in an effort to oxidatively remove CO and hydrocarbons from waste gas streams, especially sulfur-containing waste gas streams. Many of the known catalyst systems have met with failure and/or poor performance when placed in commercial operations.
As an example of the above problem, a known oxidation catalyst consisting of platinum-group metals on a high surface area alumina carrier deactivates rapidly in sulfur-containing flue gases at temperatures below about 460.degree. C. The deactivation is due to alumina sulfate formation and subsequent loss of catalyst carrier surface area. Therefore, oxidation catalysts containing high surface area alumina cannot be used commercially for the treatment of sulfur-containing flue gases below about 460.degree. C. Ideal catalysts should be stable and durable in the presence of SO.sub.x in the flue gas.
The present invention avoids the problems of the prior art by providing improved oxidation catalyst compositions having good activity and durability for the treatment of sulfur-containing flue gas streams. The present invention provides catalyst compositions comprising carriers which interact favorably with platinum-group metals and which are resistant to reaction with oxides of sulfur and exhibit superior performance for low temperature oxidative removal of CO and hydrocarbons from waste gas streams.